1. Field of the Invention
The present invention relates to a push beam for use in highwall mining operations for increased recovery of coal or other material from a generally horizontal mine.
2. Related Art
Mining methods for coal and other minerals can be divided into two types: underground mining and surface mining. Surface mining may include strip mining, open-pit mining and mountain top removal and generally involves removing layers of earth and bedrock to expose the coal, etc., for mining. However, these methods require removal of large amounts of earth (i.e., overburden), above a coal or mineral seam or deposit to reach it, especially at increasing depths. Thus, these methods eventually become uneconomic due to the amount of earth removal needed relative to the value of the mined coal, etc.
An excavated face of a hill or mountain is often created as a result of surface coal mining operations with coal seams or layers exposed on the face. However, continued strip mining or mountain top removal may no longer be feasible because of the amount of overburden above the seam that would need to be removed. Thus, a technique referred to as “highwall mining” was developed from auger mining as a way to mine these exposed horizontal coal seams without the need for expensive removal of the overburden.
Highwall mining generally involves making long rectangular drives by an unmanned continuous miner into the coal seam from the side of the highwall face. The continuous miner will generally have a rotating cutter head at its front end to cut into the coal seam as it is advanced and a gathering means at the front end to capture the coal mined by the cutter head and direct it to a set of conveyors or augers for transport out of the mine. To advance the cutter head into the seam, a series, train or string of conveyor segments (called “push beams”) are inserted behind the cutter head one-by-one and pushed from behind by a powerhead located outside the mine. By inserting the series of push beams, highwall mining is able to advance the cutter head up to about 1000 feet (or 300 meters) into these seams to mine and retrieve coal. Multiple drives are performed in parallel to recover coal along the exposed seam. These parallel mines (or drives) are typically spaced apart a sufficient amount such that a pillar or rib of the seam is left in place between neighboring mines to support the weight of the overburden and keep it from collapsing. After mining is complete, the mines may also be filled with material to provide further support and reduce hazards.
Highwall mining is considered to be a more surgical operation and better for the environment than other surface mining techniques because much of the earth is left in place and undisturbed. However, while effective at removing coal from deep narrow mines, highwall miners do tend to leave residual amounts of coal cut from the mine (referred to as “fines”) near the sides of the mine (i.e., between the push beam and the side or “rib” of the mine) as well as on the bottom of the mine. This residual coal is generally not captured by existing miners. The small amount of residual coal or fines left behind can be substantial in amount over the length of the mine hole. It is believed that about 60-120 tons of loose coal per mine (or about 8-30 tons per 100 feet of mine) is left behind typically by highwall mining. While this may amount to lost revenue due to its lack of recovery, it is currently challenging and not cost-effective to recover this coal. Because the mines are unsupported, maimed operations to recover it cannot be performed after highwall mining is complete.
Accordingly, there is a need in the art for a suitable and cost-effective apparatus and method for the recovery of this residual coal or fines that would otherwise be left behind by highwall mining.